By A. Lüscher, J. Klötzli, W. Kessler and U. Schaffner
The specific aims of the IWMPRAISE project in Switzerland are
- To develop and evaluate a novel approach of biological control of Rumex obtusifolius in grasslands (= biocontrol).
- To detect efficient management strategies to prevent infestation of grasslands with Rumex obtusifolus (= prevention).
We decided to concentrate our biocontrol work on the two root boring Sesiidae species Pyropteron doryliforme and Pyropteron chrysidiforme. Main reasons for this decision are that: (i) P. doryliforme was successful as a control agent against Rumex species in Australia, (ii) some promising pretests were done with P chrysidiforme in Switzerland and (iii) both species are native in Switzerland or in neighboring countries and, thus, can be applied in the open field without the risks related to the introduction of foreign organisms. Because both Rumex obtusifolius and the Sesiidae species are native to Switzerland, an inundative approach will be developped.
Sampling and rearing of the insects
A population of P. chrysidiforme was available at CABI from former collaborative projects. In contrast, a starting population of P. doryliforme had to be sampled in Spain. Searching field sites, planning and carrying out the sampling of the insects and bringing them to Switzerland for rearing was the main activity of this winter and spring. Since the whole biocontrol part of the next years will depend on a successful rearing of the two Sesiidae species this was a key step. Not only the sampling but also the rearing were successful. Thus, we have already insects to carry out some detailed studies this summer and autumn.
The first two experiments were planned and will be set up during the next weeks.
Larval behavior experiment: The first experiment will be a observational study, where the behavior of the larvae will be studied. The aim is to test whether there is cannibalism among the larvae. Cannibalism would be disadvantageous for the efficiency of our target control agencies P. doryliforme and P. chrysidiforme because it would restrict the number of larvae feeding on the roots of the weed Rumex obtusifolius. The behavior of the larvae will be studied under standardized and controlled conditions on pieces of Rumex obtusifolius and Rumex pulcher roots in petri dishes. We will study intra- and inter-specific cannibalism to get knowledge whether a mixed application of the two Pyropteron species on Rumex plants could be an successful option.
Infestation experiment: The second experiment will test the efficiency of the two Pyropteron species to infest the roots of Rumex plants i.e. how many larvae infest the roots of a Rumex plant. This experiment will be a common garden experiment on potted plants growing outdoor. Thus, compared to the strictly controlled larval behavior experiment described above, the infestation experiment will be a first step towards “real world” conditions of farmers fields. Again we will study the infestation efficiency of P. doryliforme alone, P. chrysidiforme alone and a mixed application of the two Pyropteron species. The technique of the application of the Pyropteron species will follow the tooth stick method (30 eggs of the insects glued on a tooth stick which is stuck besides the target plant; see Photos), which was evaluated as successful in pretests.
The prevention part of the Swiss contribution to IWMPRAISE complements the biocontrol part by being distinct in three ways. First, it is concentrating on the prevention of weed problems and not on the regulation of existing weed problems. Second, it is searching for existing management strategies to prevent the establishment of weed populations instead of developing new techniques / strategies. Third, it is concentrating on on-farm surveys and farmer interviews and is not carrying out detailed manipulative experiments. It is planned that such a survey will be carried out in 2019 addressing specifically the prevention of problems with Rumex obtusifolius. The detailed planning and the search for the farm plots will start this autumn (2018). The design of the Swiss survey will be according to the successful surveys the research group has done in earlier years on the two poisonous weed species Senecio jacobaea and Senecio aquaticus.
Collaboration with stakeholders and project partners
We decided that the strategy of stakeholder interaction and knowledge transfer of the Swiss project should base on involving and informing main actors in extension and knowledge transfer, which then should act as the multipliers of the new knowledge. The main actor for knowledge exchange and extension related to grassland in Switzerland is the AGFF (Swiss grassland society). It is a platform, with members of the Federal Office of Agriculture, seed companies, farmers, extension specialists, agricultural colleges and universities. The technical commission i.e. the stakeholder board of AGFF was informed about the IWMPRAISE activities in Switzerland. This resulted in an interesting discussion which brought up two important points for our activities. First we will get support from AGFF members to find interesting field plots and farms for the survey on “prevention of Rumex obtusifolius problems”. Second, the members of the AGFF stakeholder board expressed their interest that we should carry out a comparable survey about “prevention of problems with Juncus species”. We decided that we will add such a survey to our program if time and resources will allow.
Collaboration with IWMPRAISE partners of other countries was started and concerns both the biocontrol and the prevention part of the project.
The biocontrol part will contain common experiments together with our Slovenian partners. This aims at testing the robustness of the newly developed technique over different climatic conditions. The common protocol for the experiments was exchanged. The biggest efforts were put into the rearing of insects to be used by our Slovenian partners in their experiments. Last week members of the Slovenian partner visited Switzerland and brought back home all the insect material needed for their experiment and to start rearing of the insects in Slovenia.
The second collaboration intends to carry out the survey on “prevention of Rumex obtusifolius problems” together with our IWMPRAISE partners in United Kingdom and in Slovenia. All partners agreed to collaborate, and the detailed planning of the common protocol will be done in autumn in parallel to the development of the protocol to be applied in Switzerland.